Currently criteria for vertical transmission have not been developed. Based on limited data, viremia rates in patients with Covid-19 appear to be low and transient, suggesting placental seeding and vertical transmission are unlikely (35). In a few recent review articles on pregnant women with Covid-19, no cases of vertical transmission have been registered (36-38). A few newborn Covid-19 cases have been reported based on elevated Immunoglobulin M levels and/or pneumonia on days 1 or 2 of life, with either negative or not performed Covid-19 testing on fetal blood, amniotic fluid, and placenta (39-42). However, it is not reliable to diagnose congenital Covid-19 based only on Immunoglobulin M detection because Immunoglobulin M assays can be false positive and cross reactivity may occur. The most likely cause of positive Immunoglobulin M in many of those cases could be related to early infant infection due to postnatal contact with infected parents rather than fetal transmission (43).
Even though there is no reliable data to confirm vertical Covid-19 transmission, the Centers for Disease Control and Prevention recommend that newborns born to mothers with known Covid-19 at the time of delivery should be considered to have suspected Covid-19 and should be tested and isolated from other healthy infants (44). It is equally important to ensure that a neonate with critical CHD born to a mother with Covid-19 is managed in a timely manner and that testing for Covid-19 does not prolong or delay transfer to a tertiary center with a neonatal CHD ICU able to deliver high quality and timely management of critical CHD.